You can use HashSet<T>. The HashSet<T> class provides high-performance set operations. A set is a collection that contains no duplicate elements, and whose elements are in no particular order.
You may want to look into the concept of Command Query Separation. I wouldn’t worry about typed repositories for lookup values, but I’d still probably use DTO type classes over datasets etc… You may want to spend some time reading Greg Young’s blogs starting from this one to the present. He doesn’t talk about filling … Read more
You can iterate through the set of key-item groups and read off the keys, e.g. var keys = myLookup.Select(g => g.Key).ToList();
There are two approaches: using an Internet service and using some kind of local list (perhaps wrapped in a library). What you want will depend on what you are building. For services: http://www.hostip.info/use.html (as mentioned by Mark) http://www.team-cymru.org/Services/ip-to-asn.html For lists: http://www.maxmind.com/app/geoip_country (as mentioned by Orion) You could roll your own by downloading the lists from … Read more
Generally you should only use enumeration where there is a clear set of items that will not change, e.g. primary colours, or continent names. Otherwise lookup tables with appropriately implemented foreign keys are pretty much always the best option. There is a possible variation on the lookup table option where you potentially have a large … Read more
I believe to check if a key exists in a hash you just do if (exists $strings{$string}) { … } else { … }
You can use $toObjectId aggregation from mongodb 4.0 which converts String id to ObjectId db.role.aggregate([ { “$lookup”: { “from”: “user”, “let”: { “userId”: “$_id” }, “pipeline”: [ { “$addFields”: { “userId”: { “$toObjectId”: “$userId” }}}, { “$match”: { “$expr”: { “$eq”: [ “$userId”, “$$userId” ] } } } ], “as”: “output” }} ]) Or you … Read more
using System; using System.Collections.Generic; using System.Diagnostics; using System.Linq; using System.Security.Cryptography; namespace HashsetTest { abstract class HashLookupBase { protected const int BucketCount = 16; private readonly HashAlgorithm _hasher; protected HashLookupBase() { _hasher = SHA256.Create(); } public abstract void AddHash(byte[] data); public abstract bool Contains(byte[] data); private byte[] ComputeHash(byte[] data) { return _hasher.ComputeHash(data); } protected Data256Bit GetHashObject(byte[] … Read more
Intrinsic functions are really fast, but still are insufficient for a truly cross-platform, compiler-independent implementation of log2. So in case anyone is interested, here is the fastest, branch-free, CPU-abstract DeBruijn-like algorithm I’ve come to while researching the topic on my own. const int tab64[64] = { 63, 0, 58, 1, 59, 47, 53, 2, 60, … Read more